1. Field of the Invention
The present invention relates to a compensation value setting device and compensation value setting method, and is preferably applied to a recording and reproducing device that records and reproduces data from an optical disc, for example.
2. Description of the Related Art
In order to record and reproduce data from an optical disc, a recording and reproducing device usually uses the combination of the following methods: Partial Response Maximum Likelihood (PRML), which is one kind of partial response equalization, and maximum likelihood decoding, such as Viterbi decoding. When it adjusts sampling phase drift, track offset or the like, the recording and reproducing device writes trial recording bits, or a string of bits for recording test, on a data recording surface of an optical disc, and then reads out them from the data recording surface as analog readout signals, which are then supplied to a PRML circuit. The PRML circuit sequentially performs the processes of partial response equalization and maximum likelihood decoding to the readout signals to reproduce binary decoded data or the trial recording bits.
At this time, the recording and reproducing device synchronizes the recording sequence and the reproducing sequence, both of which are acquired by the PRML circuit. The recording and reproducing device subsequently calculates the differences of the likelihoods of the path of the reproducing sequence, which corresponds to the recording sequence whose Euclidean distance is smallest as a result of maximum likelihood decoding, and then sorts out the differences to obtain a standard deviation. Based on those differences and the standard deviation, the recoding and reproducing device adjusts sampling phase drift, track offset and the like such that the standard deviation becomes smallest (see Jpn. Pat. Laid-open Publication No. H10-21651 [Pages 1 and 2], for example).